Idle time keyer



Nav. 12, 1935 J. x.. cALLAHAN Erm.' 2,020,322

IDLETIME KEYER v Filed oct. so, 1933 2 `sheetssheet 1 mm' fam/wmf ATTRNgY Nov. 12, 1935. -J. L. CALLAHAN la'r AL 2,020,822

IDLE TIME KEYS-R Filed Oct. 30, 1935 2 Sheets-:Sheet 2 "INVENTORS Patented Nov. "12, 1935 PATENT OFFICE mLE 'rma sarna John L. Callahan. Brooklyn' and vincent n. Brown, Ozone Park, N. Y., assigner-s to Radio Corporation of America, a corporation of Delal Application october s0. 1933, serial No. 095,766

9 claims. (ci. 11sai This invention comprises an idle time keying arrangement for use on radio circuits.

In communication by radio it is frequently necessary, in order to maintain circuit contact. for the attendant at the receiving station to check the tuning adjustment of the receiver with the transmitter. When message signals are being sentover the radio channel it is the practice to utilize these same signals for the supervision of the circuit, but during idle 'time periods it is customary to transmit 'frequent test signals to maintain a loontinuous assurance that the overall circuit is-functioning; otherwise, some adjustment of `either the transmitter or receiver l5 might x change during theidle time period, a condition which mightconsequently result in no response at thereceiver when the transmitter resumes operation.4

Heretofore, in the usev of automatic telegraph transmitters, it has been customary to permit.

the pecker pins or flngersofl the automatic telegraph transmitter to function continuously to i send out positive and negative signals over the line to the radiotransmitter' during idle time 5 periods.' 'I'his method of operation, it has been found, is `wasteful of energy andv results in increased cost of operation.

The present invention overcomes the foregoing disadvantage and provides an emcient and less costly arrangement for transmitting test signals during the idle time periods, and this is accomplished, in accordance with one embodiment, by the provision of a key anda continuously operating cam arrangement, whereby the .5 line circuit is disconnected from control ofthe pecker pins inthe automatic telegraph transmitter and connected instead to a c am arrangement upon the operation of a key at the ter- I mination of the message signals. A feature of the present invention resides inthe active association ofthe key with the tape guide wheel which maintains the tape in position for operative association with the pecker pins whereby with one operation, as the guide wheel is raised to disengage the tape from the transmitter pins, the key is caused to function automatically.

In the accompanying drawings wherein like reference characters illustrate like parts, Figures 1 and 2 diagrammatically illustrate two different embodiments of the present invention. Two similar types of automatic transmitters have been shown in the two igures. only the necessary portions of which have been illustrated to enable an ,understanding of the invention, the onel shown in Figure 1 resembling generally the Wheatstone transmitter 'which is well known and adequately described in H. H. Harrisons book on Printing Telegraph Systems and Mechanisms" page 176, published 1923 by Longmans Green & Company, London, England, to which reference is made for 5 a more complete description thereof, and the other shown "in Figure 2 being of the Creed manufacture, also well known in the art. These two types have been illustrated since they are most generally employed y in telegraphy, although it 10 is to be understood that other types of automatic telegraph transmitters functioning in the same general manner will do equally as well.

Referring' to Figure 1, there is shown a transmitter which is driven at uniform speed by an 16 electric motor, not shown, connected to the mo-lJ tor drive shaft l whiclnthrough .suitable gearing 2, 3, drives an eccentric 1, in.turn actuating.

" through'a link l0, a rocking lever B which ispivoted at 9. 'I'he bell crank levers I2 land Il 20v pivoted ony the rod II are rocked against the restraint of retractile springs I6, Il by the oscillations of the rod I9 carried by the lever 8. 'I'he ypecker pins or fingers Il and Il which move in unison are designed to enter the perforations 25 in the code message tape I8 upon the .upward movement of the 4oscillating bar I9. It is understood, of course, that the pins enter the outer perforations, the center row of uniformly spaced -perfor-ations being engaged by the sprocket feed 30 l wheel 20. When pins Il and Il pass through the outer perforations-in the tape and project into the spaces between the blades or ribs of the guide g ,wheel 2|.-the bell crank levers l2, il will rock 35? on the pivot bar Il an amount sufficient to close the contact points 22, 23 against the contactl points, 25, respectively. On the other hand, if one or both of the pins do not register with the perforations on the upward stroke, but are 40 stopped bystrikin'g against -the tape, the corre' sponding lever or levers will be arrested before the contacts on their lower ends engage the con- .y

tact studs.- It will be observed that either pin may pass through a perforation while the other .45 generally simultaneously engages the non-perforated part of theA tape so that one pair of contacts -v Y ment herein indicated as 26 from which a connection extends over wire 21 to cable 28 to the 55 distant keye'r andradio transmitter which is in circuit with the antenna 29. The connection of lead 21 from the automatic telegraph transmitter to the cable 28 is made through the upper contact of a key 30 which is arranged to normally rest in the position shown'in the drawings against the extension on the guide wheel when the automatic transmitter is operating. The lower contact of key 30 is connected through a lead 3l to the armature of a key 32 which is conditioned to rest on the periphery of a continuously rotating cam 33 which is mechanically linked `through suitable gearing 34 and 35 to the motor drive shaft I. This has been indicated in the drawings by means of the dotted lines 36. It will be understood, of course, that, if desired, a separate motor may be provided for the disc since the operation thereof need not be synchronized with the main shaft. Cam 33 is preferably made of insulating material and consists of a small disc uponV the periphery of which are cut the required idle time characters. As the disc revolves, key 32 is arranged to alternately engage the upper and lower contacts 31 and 38 towhich are supplied positive and negative potentials as shown.

In the operation of the device during idle time periods when it is not desired to transmit message waves, the guide wheel 2l may be raised by the transmitter operator, automatically by turning the knurled knob of the time key 3G to automatically move the same out of vposition in the direction indicated by the arrow, to thereby swing 2l around its pivot bar away from the tape. Simultaneously, the armature of the key 30 will disconnect the radio channel cable 28, from its upper contact in circuit with lead 21 to the lower contact in circuit with the lead 3l extending to key 32 and cam 33. The continuous rotation of cam 33 will thereupon cause to be transmitted over channel 28 to the distant radio transmitter alternate positive and negative impulses or, if desired, interrupted tone in accordance with any desired code character cut into the disc, and at predetermined intervals. In this manner, the

code letters of a particular transmitter may easily y be transmitted during the idle periods.

,Y Figure 2 illustrates a preferred embodiment of the invention wherein there is provided a more simple and compact automatic telegraph transmitter arrangement of the Creed type. In this case the cam 33 is directly geared, as shown, to the motor drive shaft I, and a control relay 31' is employed to transmit message signals over the cable 28. The switching between traflic and idle time keying is here done between the auto base and the main control rel'ay 31 instead of between the cable 28 and the relay equipment as shown in Figure l. In the automatic transmitter two bell crank levers 50 and 5I connected to the pecker pins II and I3 and to the frame of the autohead control the movements of the control relay 31', one side of which is connected to the frame over lead 52 andthe other side to ground or neutral.

The upward movement of the selecting pecker Ypins Il and I3 is controlled by a rocking cam,

not shown, which is linked to the pins, and by the perforations in the tape I8. Power is transmitted to the rocking cam in well known manner through an eccentric arrangement and to the sprocket feed wheel 20 from an electric motor over drive shaft I. When a signal hole occurs in the tape, one of the selecting pecker pins Ill or I3, depending upon which is the marking or the spacing pin, is arranged to pass through it and one of the bell crank levers 50 or 5I moves either l accenna to the right or left, causing its associated contact point 52 or 53 to engage with either the positive battery contact point 54 or the negative batterycontact point 55 and thus cause the operation of control relay 31'. the pecker pins are caused to move up and down alternately through 'the action of the rocking cam assisted withthe springs 60, causing relay 21 to follow a continuous reversal of polarity.

Key 3E) herein comprises a knurled knob 56 10 and a double throw arrangement which connects the positive and negative supply on the leaf springs d5 and 46 to either the main signaling contacts 54 and 55 or to the idle time keyer cam contacts 31 and 38. This double throw device is 15 operated by the movement of the knob 56 against the extended lever of the tape idling wheel arm 2l which, in turn, acts on a lever 5.1 pivoted at 58. Spring 6I acts to normally keep the double throw device in the position indicated. Any 20 movement of the knob 56 which brings the key 3D downward to raise the guide wheel will raise the portion of the lever beyond the pivot 58 upward against the action of yspring 6I and thus operate the device to its other position. The dotted lines 25 show the lever and the key in its other position.

In order to provide idle .time keying for either of two types of control line services, one of which is the so-called tone control and the other direct current control, the marking and spacing con- 30 tacts and the armature of control relay are brought to a triple pole double throw switch 59 which in one position connects the automatic transmitter in an obvious manner to line 28/ for direct current operation, and in the other posi- 35 tion to a tone pair for tone line control.

In actual practice, the idle time keying device is attached to the automatic transmitter gear shaft contacts, the keying arrangement being located directly inside of the automatic trans- 40 'mitten and the keying disc 33 is fastened directly on the automatic transmitter to the large gear which drives the tape star wheel 20, the double throw arrangement and the contacts 38 and 31 also being attached to the transmitter. 45

It has been found that a considerable saving of energy can be obtained with this invention, the amount of which varies with such factors as the speed of rotation of the disc and the spaces between cuttings on the periphery of the cam. 50 The invention makes possible a reduction in the number of continuous voltage polarity reversals across the control relay winding.

An important advantage of the invention is the semi-automatic character of the idle time 55 y key control which requires no special attentiony on the part of the operating personnel in order to shift from direct to idle time keying. Thus, when traffic circuits are busy the operating personnel is not required to keep in mind the ne- 00 cessity of shifting from vdirect to idle time keying when the message is idle.

It is to be understood, of course, that various p modifications may be made, such 'as arranging In the absence of any tape, 5

varranged in one position to associate said message channel with said automatic transmitter for control by said tape for the transmission of message signals thereover and in another position in response to movement of said guide element to associate said channel with said rotating cam for the transmission of test characters thereover.

2. A radio transmitting circuit comprising a message channel, an automatic` telegraph transmitter having a message tape and a guide element therefor, a continuously rotating cam driven from the same shaft as said telegraph trans-v mitter and arranged 'to cause the transmission of test characters, and a key linked with said guide element and arranged in one position to associate said message channel withv said automatic transmitter for control by said tape and in another position to operatively associate said message channel with said cam.

3. A radio transmitting circuit comprising a message channel, an automatic telegraph transmitter having a message tape and a guide element therefor, means associated with said transmitter for causing the transmission of predetermined test characters, and a key operatively associated with said guide element and responsive to a movement of said guide element in one position to connect said message channel to said automatic transmitter for cont-rol by said tape and responsive to movement of said guide element in another position to connect said channel to said means.

4. In combination in a communication system, a line, an automatic telegraph transmitter having a message tape and a guide wheel therefor, means associated with said transmitter for causing the transmission oi' test characters having length shorter than those oi' the message characters, and a key operatively associated with said guide wheel and arranged in one position of said guide wheel to connect said line to said transmitter for receiving message signals therefrom and in another position to connect said line to said means.l

5. In combination in a communication system, a line, an automatic telegraph transmitter having a message tape and means for maintaining said tape in operative association with said transmitter,` said means having at least two degrees of freedom, rotating means for generatingv test characters, and switching mechanism responsive to movement of said rst means in one direction for connecting said line to said transmitter .for receiving message signals therefrom and to movement in another direction for connecting said line to said rotating means whereby test characters are sent out over said line.

. 6. A radio transmitting circuit comprising a message channel, an automatic cable transmitter 5 having a message tape and a guide wheel therefor, a cam associated with said transmitter and arranged to cause lthe transmission of predetermined test characters, andl a key operatively associated with said guide wheel and arranged in 10 one position to connect said channel to said automatic transmitter and in another position to connect said channel to said cam.

7. A radio transmitting circuit comprising a message channel, an automatic cable transmitl5 ter having a message tape and a. guide wheel therefor, a continuously rotating cam driven from the same shaft as said cable transmitter and arranged to cause the transmission of test characters, and a key operatively associated with said 20 f guide wheel and arranged in one position to connect said message channel to said automatic transmitter and in another position to connect said message channel to said cam.

8. A radio transmitting circuit comprising Va message channel, an automatic telegraph transmitter having a message tape and a guide wheel therefor, a cam associated with said transmitter and arranged to causethe transmission of test characters. a control relay in circuit with said message channel, and a double throw key mechanically connected to said guide wheel and arranged in one position to operatively associate said control relay with said automatic transmitter for being controlled by said tape and in another 35 position to operatively associate said control relay with said cam.

9. A radio transmitting circuit comprising two message channels one adapted for direct current control and the other adapted for tone control, 40 an automatic telegraph transmitter having a message tape and a de wheel therefor, a cam associated with sai; transmitter and arranged to cause the t ion of test characters, a control relay, a two position key mechanically con- 45 nected to said guide wheel and arranged in one position toy operatively associate said control relay with said automatic transmitter for control by said tape and in the other position to operatively associate said control relay with said cam, 50 and switching mechanism for connecting said control relay with either of said two message channels.

JOHN L. CALLAHAN. VINCENT H. BROWN. 65 

